MTAD

1. ENDODONTICS
MTAD
A Review of a Promising Endodontic Irrigant
Zahed Mohammadi, D.M.D., M.S.D.
ABSTRACT
The essential role of microorganisms in the initiation
and perpetuation of pulp and periapical pathosis has
been well documented. The major objective in endo-
dontic therapy is to disinfect the entire root canal sys-
tem. Considering the complex anatomy of the root
canal system, complete elimination of bacteria by
cleaning the root canal with instrumentation alone
is unlikely. Therefore, an appropriate antimicrobial
irrigant is needed to decrease the microbial load, es-
pecially in necrotic and retreatment cases. Another
important issue in endodontics is the smear layer. Al-
though there is no general consensus on removal of
the smear layer, it seems that removing it enhances
the sealing ability of the root canal filling. MTAD is
an endodontic irrigant with both antibacterial and
smear layer removal abilities. The aim of this paper is
to review these different aspects of MTAD.
Microorganisms and their byproducts play an essential role in the
development and perpetuation of pulp and periapical diseases.^"^
The elimination of microorganisms from infected root canal sys-
tems is a complicated task. Numerous measures, including the use
of various instrumentation techniques, irrigation regimens and
intra-canal medicaments, have been described to reduce the mi-
crobial load inside the root canal system. There is no solid evidence
that demonstrates that mechanical instrumentation alone results
in a bacteria-free root canal system. When the complex anatomy of
the root canal system* is considered, this is not surprising.
In vitro and clinical evidence have shown that mechani-
cal instrumentation leaves significant portions of the root canal
walls untouched,' and complete elimination of bacteria by in-
strumentation alone is unlikely to occur.* It is assumed, but not
demonstrated, that any pulp tissue left in the root canals can
serve as nutrient for any remaining bacteria. Furthermore, tis-
sue remnants also impede the antimicrobial effects of root canal
irrigants and medicaments. Therefore, some form of irrigation
and disinfection is necessary to remove residual tissue and to kill
microorganisms.
Another issue of great importance during root canal treat-
ment is the smear layer. The effect of the smear layer on the mi-
croleakage of obturated root canals is still controversial. Some
authors suggest that keeping the smear layer may block the den-
tinal tubules and limit bacterial or toxin penetration by altering
the dentinal permeability.''"' On the other hand, some believe
that the smear layer must be completely removed from the sur-
face of the canal wall because it can harbor bacteria and can be
detrimental to the effective disinfection of dentinal tubules by
The New York state Dental Journal • AUGUST/SHPTEIVIBER 2O12 47

2. preventing irrigant and medicaments from penetrating into the
dentinal tubules. It can also act as a barrier between obturating
materials and the canal wall and, thus, interfere with the forma-
tion of an appropriate seal.''°"''^
A systematic review of in vitro studies showed that smear
layer removal improves the fiuid-tight seal of the root canal sys-
tem." Prior to the introduction of MTAD, there was no irrig-
ant capable of removing the smear layer and disinfecting the root
canal system simultaneously. MTAD consisted of a mixture of a
tetracycline isomer (doxycycline), an acid (citric acid) and a de-
tergent (Tween-80).''''
Rationale for Local Application of Antimicrobials
While systemic antibiotics appear to be clinically effective as an
adjunct in certain surgical and nonsurgical endodontic cases,
their administration is not without the potential risk of adverse
systemic effects, particularly possibilities of allergic reactions, tox-
icity, side effects and development of resistant strains of microbes.
Systemic administration of antibiotics relies upon circulation to
bring the active drug to an infected site that
may no longer possess a normal vascula-
ture, including the necrotic pulpless tooth
and the periradicular tissues; therefore, the
local application of antibiotics may be a
more effective mode of delivery."
as effective as citric acid in removing the smear layer.^^ Another
study showed that teeth with retrograde IRM or amalgam fillings
placed following doxycycline irrigation of the retro-cavities had
significantly less dye leakage.^"
Using an agar diffusion test, Carson et al.^* evaluated the
antimicrobial activities of 6% and 3% sodium hypochlorite
(NaOCl), 2% and 0.12% chlorhexidine gluconate (CHX), and
0.01% and 0.005% doxycycline (Doxy) on Peptostreptococcus mi-
cros, Prevotella intermedia, Streptococcus sanguis and Lactobadllus
acidophilus. For P. micros, P. intermedia, S. sanguis, both concen-
trations of doxycycline were more effective than other agents.
For L. acidophilus, the effectiveness of doxycycline was less than
other materials. Pinheiro et al." found that 85.7% of Enterococcus
faecalis isolates from canals of root-filled teeth with periapical le-
sions was susceptible to tetracycline and doxycycline. Chai et al.^*
showed that oxytetracycline was 100% effective in eliminating £.
faecalis biofilm.
Tetracyclines
Tetracyclines (including tetracycline-HCl,
minocycline, demeclocycline and doxycy-
cline) are a group of broad-spectrum antibi-
otics that are effective against a wide range of
micro-organisms.'''' They are bacteriostatic in
nature.''"' This property may be advantageous
because, in the absence of bacterial cell ly-
sis, antigenic byproducts, such as endotoxin,
are not released.''* Tetracyclines have many
other unique properties, such as the inhibition of mammalian col-
lagenases, which prevents tissue breakdown,'"^'''' and the inhibition
of clastic cells'^"'" that results in anti-resorptive activity.^' Infiam-
matory diseases such as periodontitis include a pathological excess
of tissue collagenases that may be blocked by tetracyclines, leading
to enhanced formation of collagen and bone formation.^"
Tetracyclines have been used to remove the smear layer from
instrumented root canal walls,^^'^^ for irrigation of retrograde
cavities during periapical surgical procedures^" and as an intra-
canal medicament.^^ Barkhordar et al.^'' showed that doxycycline
HCl eliminated the smear layer in a concentration-dependent
manner from the instrumented root canal walls. Results showed
that 100 mg/ml doxycycline HCl was more effective than lower
concentrations in removing the smear layer. A scanning electron
microscopy (SEM) study demonstrated that tetracycline HCl was
Another issue of great
importance during root
canal treatment is the
smear layer. The effect
of the smear layer on
the microleakage of
obturated root canals
is still controversial.
Substantivity of Tetracyclines
Tetracyclines readily attach to dentin and
are subsequently released without losing
their antibacterial activity.^"* This property
creates a reservoir of active antibacterial
agent, which is then released from the den-
tin surface in a slow and sustained manner.
In periodontics, several studies have been
conducted on the antibacterial substan-
tivity of tetracyclines. A periodontal study
showed that both concentrations of tetra-
cycline demonstrated residual antibacterial
activity and the antibacterial substantivity
of the three solutions in descending order
was: 50 mg/ml tetracycline > 10 mg/ml
tetracycline > 0.12% CHX.-^ In the field of
endodontics, Abbott et al.'* demonstrated
that tetracyclines form a strong reversible
bond with hard tissues and that they exhibit slov/ release over an
extended period of time. Other studies have sho'OTi the substan-
tivity of doxycycline for up to four weeks.^'''°
BioPure MTAD
Antibacterial activity
BioPure (Dentspfy, Tulsa Dental, Usa, OK), otherwise known as MTAD
is a root canal irrigant introduced by Torabinejad et al. in 2003.^*
The solution is a mixture of 3% doxycycline, 4.25% citric acid and
a detergent (0.5% Polysorbate 80)."
Several studies have evaluated the effectiveness of MTAD
for disinfection of root canals. Torabinejad et al. have shown that
MTAD is able to remove the smear layer^'' and is effective against
£. faecalis.^^-^'^ Shabahang et al.^* demonstrated that the use of
MTAD was more effective than 5.25% NaOCl in disinfecting root
48 AUGUST/SEPTEZVIBER 2O12 • The New York State Dental Journal

3. canals. However, Tay et al.'' found that when MTAD is applied
to 1.3% NaOCl-irrigated dentin, its antimicrobial substantivity
is reduced. They attributed this phenomenon to the oxidation of
MTAD by NaOCl in a manner similar to the peroxidation of tet-
racycline by reactive oxygen species.
Torabinejad et al.'^ compared the antibacterial effects of
MTAD with those of NaOCl and EDTA by using standard in vitro
microbiological techniques and reported that MTAD was signifi-
cantly more effective against E. faecalis. Kho and Baumgartner^*
compared the antimicrobial efficacy against £ faecalis of 1.3%
NaOCl/BioPure MTAD with that of the combined alternate use
of 5.25% NaOCl and 15% EDTA for root canal irrigation. Their
findings showed consistent disinfection of infected root canals
when a combination of 5.25% NaOCl/15% EDTA was used.
However, the combination of 1.3% NaOCl/BioPure MTAD left
nearly 50% of the canals contaminated with E. faecalis. In an-
other study, the antimicrobial effect against E. faecalis of MTAD,
two of its components (doxycycline and citric acid) and sodium
hypochlorite were assessed in two in vitro models using two dif-
ferent methods. In the tooth model, NaOCl and doxycycline were
more effective than the control in killing E. faecalis at shallow
bur depths into dentin; but at deeper bur depths, the NaOCl was
superior. In the agar diffusion model, NaOCl produced less inhi-
bition of bacteria than MTAD or doxycycline.'^
Ghoddusi et al.'* evaluated the effect of MTAD as a final irri-
gant on bacterial leakage of the root canal and its interaction with
two conventional root canal sealers (AH-Plus or Rickert). Accord-
ing to their findings, it took longer for bacteria to penetrate when
either EDTA or MTAD was used for smear layer removal. Fur-
thermore, the root canals obturated with AH-Plus showed signifi-
cantly longer duration of resistance to bacterial penetration than
canals obturated with Rickert.
Using the zone of inhibition test and Enterococcus faecalis as
a test microorganism, Davis et al." demonstrated that BioPure
MTAD showed significantly more zones of microbial inhibition
than 5.25% NaOCl, 2% CHX, and Dermacyn (Oculus Innovative Sci-
ences, Petaluma, CA). Newberry et al.''° determined in vitro the anti-
microbial effect of MTAD as a final irrigant on eight strains of
E. faecalis and measured the minimum inhibitory concentration
(MIC) and the minimum lethal concentration (MLC) of MTAD.
After irrigating with 1.3% NaOCl, the root canal and the exter-
nal surfaces were exposed to MTAD for five minutes. The results
showed that this treatment regimen was effective in completely
eliminating growth in seven of eight strains of E. faecalis. The
MIC/MLC tests showed that MTAD inhibited most strains of E.
faecalis growth when diluted 1:8192 times and killed most strains
of E. faecalis when diluted 1:512 times.
Shabahang et al."*^ evaluated the effect of the addition or
substitution of chlorhexidine for doxycycline and compared these
three formulations in their ability to disinfect extracted human
teeth infected with E. faecalis. The results showed that although
the addition of chlorhexidine did not negatively impact the ef-
ficacy of MTAD, the substitution of this antimicrobial agent for
doxycycline significantly reduced the efficacy of the solution.
Substantivity of MTAD
As stated earlier, tetracyclines (including doxycycline) readily at-
tach to dentin and are subsequently released without losing their
antibacterial activity.^^ The presence of doxycycline in MTAD sug-
gests that MTAD may have some substantive antimicrobial ac-
tion." In an in vitro study, Mohammadi and Shahriari*^ showed
that the substantivity of MTAD was significantly greater than that
of CHX and NaOCl. Another study demonstrated that the sub-
stantivity of 100% MTAD was significantly greater than the two
other concentrations (10% and 1%) of MTAD.*'
MTAD and Biofilms
The term biofilm was introduced to designate the thin-layered
condensation of microbes that may occur on various surface
structures in nature. Free-floating bacteria existing in an aqueous
environment, or planktonic microorganisms, are a prerequisite
for biofilm formation.'* Such films may, thus, become established
on any organic or inorganic surface substrate where planktonic
microorganisms prevail in a water-based solution.
In dental contexts, a well-known and extensively studied bio-
film structure is established during the attachment of bacteria to
teeth to form dental plaque. Here, bacteria free in saliva (planktonic
organisms) serve as the primary source for the organization of this
specific biofilm.''* However, in endodontics, the biofilm concept has
thus far gained limited attention. It has been discussed mainly with-
in the framework of bacterial appearances on root tips of teeth with
non-vital pulps.*' Such bacterial aggregations have been thought to
be the cause of therapy-resistant apical periodontitis.**'''' Bacterial
condensation (that is, biofilms) on the walls of infected root canals
have been observed, but have not been described in great detail.**
Anti-microbial agents have often been developed and opti-
mized for their activity against fast-growing, dispersed popula-
tions containing a single microorganism.*' However, microbial
communities grown in biofilms are remarkably difficult to eradi-
cate with anti-microbial agents, and microorganisms in mature
biofilms can be notoriously resistant for reasons that have yet to
be adequately explained.*' There are reports showing that micro-
organisms grown in biofilms could be two- to 1000-fold more
resistant than the corresponding planktonic form.*' Clegg et al.'°
evaluated the effectiveness of three concentrations of NaOCl
(6%, 3% and 1%), 2% CHX and BioPure MTAD on apical dentin
biofilms in vitro. Their findings indicated that 6% NaOCl was the
only irrigant capable of both rendering bacteria nonviable and
physically removing the biofilm.
Dunavant et al.'^ evaluated the efficacy of 6% NaOCl, 1%
NaOCl, Smear Clear, 2% CHX, REDTA and BioPure MTAD
against E. faecalis biofilms using a novel in vitro testing sys-
The New York State Dental Journal • AUGUST/SEPTEMBER 2O12 49

4. tem. Biofilms grown in a flow cell system were submerged in
test irrigants for either one or five minutes. There was a sig-
nificant relationship between the test agent and the percent-
age kill of the biofilm bacteria. No significant relationship
between time and percentage kill was found. The percentage
kill of the bioñlm bacteria was: 6% NaOCl (>99.99%), 1%
NaOCl (99.78%), Smear Clear (78.06%), 2% CHX (60.49%),
REDTA (26.99%) and BioPure MTAD (16.08%). There was a
significant difference between 1% and 6% NaOCl and all other
agents, including Smear Clear, 2% CHX, REDTA and BioPure
MTAD. Therefore, both 1% NaOCl and 6% NaOCl were more
efficient in eliminating £. faecalis biofilm than the other solu-
tions tested.
Giardino et al." evaluated the efficacy of 5.25% NaOCl
and MTAD against E. faecalis biofilm and found that only 5.25%
NaOCl was able to disgrégate and remove the biofilm at every
tested time period.
On the whole, it seems that NaOCl is the only endodontic
irrigant that can disrupt and remove microbial bioñlm from the
infected root canals.
Smear Layer Removal
Many instrumentation techniques have been proposed to shape
root canals to facilitate their complete obturation. Less attention
has been directed toward the ability of these techniques to com-
pletely clean and disinfect the root canal system. Studies show
that currently used methods of instrumentation, especially rotary
instrumentation techniques, produce a smear layer that covers
root canal walls and the openings to the dentinal tubules."'^*
The smear layer consists of organic and inorganic substances,
including fragments of odontoblastic processes, microorganisms
and necrotic materials. The presence of this smear layer prevents
penetration of intracanal medication into the irregularities of
the root canal system and the dentinal tubules and also prevents
complete adaptation of obturation materials to the prepared root
canal surfaces."
Various organic acids, ultrasonic instruments and lasers
have been used to remove the smear layer. Based upon available
evidence, it seems that these agents and methods do not provide
complete disinfection of the root canal spaces in all cases when
used in one-visit root canal therapy. Because of the ineffectiveness
of these techniques, many practitioners rely upon the placement
of Ca(OH)2 in the root canals to assist in canal disinfection.^'-"
As a result, root canal therapy has to be performed in more than
one appointment.
For the first time, Torabinejad et al.'* showed that MTAD
was an effective solution for the removal of the smear layer and
did not significantly change the structure of the dentinal tubules
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5O AUGUST/SEPTEIVIBER 2O12 • The New York State Dental Journal

5. when canals were irrigated with sodium h5^ochlorite and under-
went a final rinse of MTAD. In another study, they showed that
although MTAD removed most of the smear layer when used as
an intracanal irrigant, some remnants of the organic component
of the smear layer remained scattered on the surface of the root
canal walls.'^
The effectiveness of MTAD to completely remove the smear
layer was enhanced when low concentrations of NaOCl were
used as an intracanal irrigant before the use of MTAD as a fi-
nal rinse. This regimen did not seem to significantly change the
structure of the dentinal tubules.'* Tay et al." revealed that both
irrigants created a zone of demineralized collagen matrices in
eroded dentin and around the dentinal tubules, with the mildly
acidic BioPure MTAD being more aggressive than EDTA. These
demineralized dentin zones create the opportunity for dentin
hybridization by infiltration of hydrophilic
adhesives/sealers. However, the potential
consequences of compaction of hydropho-
bic sealers against air-dried, collapsed col-
lagen matrices and hydrolytic degradation
of incompletely infiltrated matrices remain
unresolved. In an ultrastructural study, Tay
et al.'° showed that BioPure MTAD cre-
ated a thicker demineralized dentin ma-
trix (5-6 micrometers) than EDTA (1-2
micrometers). De-Deus et al.*' found that
the demineralization kinetics prompted
by BioPure MTAD were significantly faster
than those prompted by a 17% solution of
EDTA.
Bone apatite has
long been known to
be a major carbonate
reservoir, providing
buffering for all acid-
base disturbances and
maintaining the body's
acid-base balance.
Effects of MTAD on Dentin
Machnick et al." evaluated the effect of MTAD on the flexural
strength and modulus of elasticity of dentin. Dentin bars were
randomly assigned to eight groups treated with various concen-
trations of NaOCl (5.25%, 2.65%, 1.31% and 0.66%), a 17% so-
lution of EDTA, MTAD, saline, or, according to a clinical protocol,
with 1.3% NaOCl and then five minutes of MTAD. Specimens
were subjected to ñexur.al strength and modulus of elasticity tests.
Findings showed no statistically significant differences between
various groups except for a reduction in fiexural strength for the
2-h MTAD group and the EDTA group. A significant reduction of
modulus of elasticity for the 2-h MTAD group, EDTA group and
0.6% NaOCl also was noted. There was no significant difference
in flexural strength and modulus of elasticity between the dentin
bars exposed to saline or MTAD when applied according to the
clinical protocol.
In summary, it seems that MTAD is suitable for clinical
use as prescribed without affecting the physical properties of
the dentin.
Buffering Effect of Dentin on MTAD
Bone apatite has long been known to be a major carbonate res-
ervoir, providing buffering for all acid-base disturbances and
maintaining the body's acid-base balance.'^ With a quite similar
chemical composition, dentin can be expected to have a corre-
sponding buffering effect on acids and bases.
Wang and Hume^* showed that dentin was a strong buffer
against acids. Buffering against alkali (NaOH) was weaker but,
nevertheless, considerable. Dentin chips weighing 250 mg were
able to keep the pH unchanged after the addition of 3 mmol of HCl
or 2 mmol of NaOH. Inorganic apatites are supposed to be mainly
responsible for the buffering effect of dentin. However, the fact
that whole dentin is a more effective buffer than hydroxyapatite
suggests that other inorganic and even organic components also
contribute to the buffering. Camps and Pashley*' found that or-
ganic components of dentin alone accounted
for 1.5% of the total buffering capacity.
The root canal milieu is a complex mix-
ture of a variety of organic and inorganic
compounds. Hydroxyapatite, the main com-
ponent of dentin, is the major representa-
tive of inorganic components present. In
addition, inflammatory exúdate, entering
the apical root canal in purulent infections,
is rich in proteins such as albumin.**
The relative importance of the vari-
ous organic and inorganic compounds in
the inactivation of root canal disinfectants
has been studied to a limited extent.** Dif-
ficulties in designing experiments that will
give reliable and comparable data were one
of the great challenges for researchers for
many years. Ultimately, Haapasalo et al.*^ introduced a new den-
tin powder model for studying the inhibitory effect of dentin on
various root canal irrigants and medicaments. Portenier et al.**
investigated the inhibitory effects of dentin and bovine serum al-
bumin (BSA) on the antibacterial activity of chlorhexidine and
MTAD and found that the presence of dentin or BSA caused a
marked delay in the killing of bacteria by both medicaments.
MTAD and Dentin Bonding (Anticollagenolytic Activity)
During the last two decades, chemical and technical advances have
contributed to increases in resin-dentin bond strength. However,
the premature loss of bond strength is one of the problems that
still affects adhesive restorations*' and markedly reduces their du-
rability.'""''^ The loss of bond strength has been attributed mainly
to the degradation of the hybrid layer at the dentin-adhesive in-
terface. Numerous publications have demonstrated this lack of
bond stability."-'*
The notion that deterioration of dentin collagen fibrils con-
tributes to the mechanism responsible for bond degradation has
The New York state Dental Journal • AUGUST/SEPTEIVIBER 2O12

6. been reported.'''^' In this context, it has been speculated that a
decreasing concentration gradient of resin monomer diffusion
within the acid-etched dentin, and a subsequent resin elution
from hydrolj^ically unstable pol3mieric hydrogels within the hy-
brid layers^^ leave the collagen fibrils unprotected and vulnerable
to degradation by endogenous metalloproteinases (MMPs). The
MMPs are a group of 23 mammalian enzymes capable of degrad-
ing all extracellular matrix components. Human dentin contains
at least collagenase (MMP-8), gelatinases MMP-2 and -9, and
enamelysin MMP-20.'''"*^ Dentin collagenolytic and gelatinolytic
activities'^ can be suppressed by protease inhibitors,''* indicating
that MMP inhibition could be beneficial in the preservation of
hybrid layers.
Tetracyclines have also been shown to inhibit mammalian
collagenases. Inflammatory diseases such as periodontitis include
a pathological excess of tissue collagenases that may be blocked
by tetracyclines, leading to enhanced formation of collagen and
bone formation. Doxycycline, a hydroxy derivative of tetracycline,
is the most potent anticollagenase antibiotic among commercially
available tetracyclines^" and is also relatively more potent against
most periodontal pathogens.^°"^^
Machnick et al." compared the effect of MTAD and phos-
phoric acid on the bond strength to enamel and dentin using a
conventional OptiBond Solo Plus dentin adhesive system and re-
ported that teeth endodontically treated vnth the MTAD protocol
for clinical use (20 min 1.3% NaOCl/5 min MTAD) might not
need any additional dentin conditioning before the application of
the dental adhesive. Garcia-Godoy et al.^'* evaluated the structure
of the hybrid layer formed after the use of EDTA or MTAD solu-
tions when used as a final fiush. Findings showed that the BioPure
MTAD hybrid layer was thicker than the 17% EDTA hybrid layer.
Both the BioPure MTAD and EDTA caused a collapse of the den-
tin matrix structure, which impeded sealer infiltration and the
formation of high-quality hybrid layer bonding. The hybrid layers
created in smear layer-covered dentin exhibited less potential for
nanoleakage than the MTAD or EDTA hybrid layers. Wachlaro-
wicz et al.*' reported that neither EDTA nor MTAD significantly
improved Epiphany-dentin bond strengths when compared with
NaOCl used alone.
On the whole, due to its broad-spectrum MMP-inhibitory
effect, MTAD can significantly improve the resin-dentin bond
stability.
Toxicity of MTAD
There is only one study regarding the toxicity of MTAD. Zhang et
al.*' examined the cytotoxicity of MTAD compared with that of
commonly used irrigants and medications. L929 fibroblasts were
grown on cell culture plates and were placed in contact with vari-
ous concentrations of test irrigants and medications. The cytotox-
icity of these materials was evaluated 24 hours after incubation
using MTT assay. Results showed that MTAD was less cytotoxic
than eugenol, 3% H2O2, Ca(OH)2 paste, 5.25% NaOCl, Peridex
and EDTA and was more cytotoxic than 2.63%, 1.31% and 0.66%
NaOCl. //.
Queries about this article can be sent to Dr. lÁohavnmadi at zahed.moham-
madi®smail.corr.
REFERENCES
1. Kakehashi S, Stanley HR, Fitzgerald RJ. The effects of surgical exposure of dental pulps in
germ-free and conventional laboratory rats. Oral Surg 1965:18:340-8.
2. Möller AJ, Fabricius L, Dahlen G, Öhman AE, Heyden G. Influence on periapical tissues of
indigenous oral bacteria and necrotic pulp tissue in monkeys. Scand J Dent Res 1981: 89:
475-84.
3. Sundqvist G. Ecology of the root canal flora. J Endod 1992:18:427-30.
4. Hess, W. Anatomy of root canals in the teeth of the permanent dentition. New York, 1925,
William Wood & Co.
5. Peters OA, Laib A, Gohring TN, Barbakow F. Changes in root canal geometry after prepara-
tion assessed by high resolution computed tomography. J Endod 2001: 27:1-6.
6. Bystrom A, Sundqvist C. Bactériologie evaluation of the efficacy of mechanical root canal
instrumentation in endodontic therapy. Scand J Dent Res 1981: 89:321-8.
7. Michelich VJ, Schuster GS, Pashley D. Bacterial penetration of human dentin in vitro. J
Dent Res 1980:59:1398-403.
8. Pashley D, Michelich VJ, Kehl T. Dentin permeability: effects of smear layer removal. J
Prosthet Dent 1981:46:531-7.
9. Safavi KE, Spangberg L, Langeland K. Root canal dentinal tubule disinfection. J Endod
1990:16:207-10.
10. Foster KH, Kulild JC, Weiler RN. Effect of smear layer removal on the diffusion of calcium
hydroxide through radicular dentin. J Endod 1993:19:136-40.
11. Lester KS, Boyde A. Scanning electron microscopy of instrumented, irrigated and filled root
canals. Br Dent J 1977;143:359-67.
12. Czonstkowsky M, Wilson EG, Holstein FA. The smear layer in endodontics. Dent Clin
North Am 1990:34:13-25.
13. Shahravan A, Haghdoost AA, Adi A, Rahimi H, Shadifar F. Effect of smear layer on sealing ability
of canal obturation: a systematic review and meta-analysis. J Endod 2007:33:96-105.
14. Torabinejad M, Khademi AA, Babagoli J, Cho Y, Johnson WB, Bazhilov K, Kim J, Shabahang
S. A new solution for the removal of the smear layer. J Endod 2003:29:170-175.
15. Gilad JZ, Teles R, Goodson M, White RR, Stashenko P. Development of a clindamycin-
impregnated fiber as an intracanal medication in endodontic therapy. J Endod 1999:25:
722-727.
16. Vemillo AT, Ramamurthy NS, Golub LM, Rifkin BR. The non-antimicrobial properties of
tetracycline for the treatment of periodontal disease. Curr Opin Perio 1994:2:111-118.
17. Pierce A, Lindskog S. The effect of an antibiotic/corticosteroid paste on inflammatory root
résorption in vivo. Oral Surg Oral Med Oral Pathol 1987: 64:216-220.
18. Pierce A, Heithersay G, Lindskog S. Evidence for direct inhibition of dsntinoclasts by a
corücosteroid / antibiotic endodontic paste. Endod Dent Traumatol 1988:4:44-45.
19. Bryson E, Levin L, Banchs F, Abbott P, Trope M. Effect of immediate intracanal placement of
Ledermix paste on healing of replanted dog teeth after extended dry times. Dent Traumatol
2002:18:316-321.
20. Barkhordar RA, Russell T. Effect of doxycycline on the apical seal of the retrograde filling
materials. J Calif Dent Assoc 1998:26:842-845.
21. Barkhordar RA, Watanabe LG, Marshall GW, Hussain MZ. Removal of the smear layer by
doxycycline in vitro. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1997: 84:420-423.
22. Haznedaroglu F, Ersev H. Tetracycline HCl solution as a root canal irrigant. J Endod 2001:
27:738-740.
23. Molander A, Dahlen G. Evaluation of the antibacterial potential of tetraq/cline or erythro-
mycin mixed with calcium hydroxide as intracanal dressing against E. faecalis in vivo. Oral
Surg Oral Med Oral Pathol Oral Radiol Endod 2003:96:744-750.
24. Carson KR, Goodell GG, McClanahan SB. Comparison of the antimicrobial activity of six
irrigants on primary endodontic pathogens. J Endod 2005:31:471-473.
25. Pinheiro ET, Gomes BP, Drucker DB, Zaia AA, Ferraz GG, Souza-Filho FJ. Antimicrobial
susceptibility of Enterococcus faecalis isolated from canals of root filled teeth with periapical
lesions. Int Endod J 2004:37:756-763.
26. Chai WL, Hamimah H, Gheng SG, Sallam AA, Abdullah M. Susceptibility of Enterococcus
faecalis biofilm to antibiotics and calcium hydroxide. J Oral Sei 2007:49:161-166.
27. Stabholz A, Kettering JD, Aprecio R, Zimmerman G, Baker PJ, Wikesjo UM. Retention of
the antimicrobial activity by human root surfaces after in situ subgingival irrigation with
tetracycline HGL or chlorhexidine. J Periodontol 1993:64:137-141.
28. Abbott PV, Heithersay GS, Hume WR. Release and diffusion through human tooth roots in
vitro of corticosteroid and tetracycline trace molecules from Ledermix paste. Endod Dent
Traumatol 1988:4:55-62.
AUGUST/SEPTEMBER 2O12 • The New York State Dental Journal

7. 29. Khademi AA, Mohammadi Z, Havaee A. Evaluation of the antibacterial substantivity of 62.
several intra-canal agents. Aust Endod ) 2006:32:112-115.
30. Mohammadi Z, Farhad A, Ardakani FE. Antibacterial substantivity of three concentrations of 63.
doxycycline in bovine root dentin infections: an In vitro study. Dent Res J 2007:4:48-52.
31. Torabinejad M, Johnson WB. irrigation solution and methods of use. US Patent & Trade
Mark Office. United States Patent Application 20030235804: December 25, 2003. 64.
32. Torabinejad M, Shabahang S, Aprecio R, Kettering JD. The antimicrobial effect of MTAD: An
in vitro investigation. J Endod 2003;29:400-3. 65.
33. Shabahang S, Pouresmai! M, Torabinejad M. in vitro antibacterial efficacy of MTAD and 66.
sodium hypochlorite. J Endod 2003:29:450-2.
34. Shabahang S, Torabinejad M. Effect of MTAD on Enterococcus /aecalis-contaminated root 67.
canals of extracted human teeth. J Endod 2003:29:576-9.
35. Tay FR, Hiraishi N, Schuster GS, Pashley DH, Loushine RJ, Ounsi HF, Grandini S, Yau JYY, 68.
Mazzoni A, Donnelly A. Reduction in antimicrobial substantivity of MTAD after initial
sodium hypochiorite irrigation. J Endod 2006:32:970-5.
36. Kho P, Baumgartner JG. A comparison of the antimicrobial efficacy of NaOGl/BioPure 69.
MTAD versus NaOCI/EDTA against Enterococcus faecalis. J Endod 2006:32:652-5.
37. Krause TA, Uewehr FR, Hahn GL. The antimicrobial effect of MTAD, sodium hypochlorite, 70.
doxycycline, and citric acid on Enterococcus faecalis. J Endod 2007:33:28-30.
38. Ghoddusi J, Rohani E, Rashed T, Ghaziani P, Akbari M. An evaluation of microbial leakage 71.
after using MTAD as a final irrigation. J Endod 2007:33:173-6.
39. Davis JM, Maki J. Bahcall JK. An in vitro comparison of the antimicrobial effects of various 72.
endodontic medicaments on Enterococcus faecalis. J Endod 2007:33:567-9.
40. Newberry BM, Shabahang S, Johnson N, Aprecio RM, Torabinejad M. The antimicrobial 73.
effect of BioPure MTAD on eight strains of Enterococcus faecalis: an in vitro investigation. J
Endod 2007:33:1352-4. 74.
41. Shabahang S, Aslanyan J, Torabinejad M. The substitution of chlorhexidine for doxycycline
in MTAD: The antibacterial efficacy against a strain of Enterococcus faecalis. J Endod 2008: 75.
34:288-90.
42. Mohammadi Z, Shahriari S. Residual antibacterial activity of chlorhexidine and MTAD in 76.
human root dentin in vitro. J Oral Sei 2008:50:63-7.
43. Mohammadi Z. Evaluation of the residual antibacterial activity of three concentrations of a 77.
new root canal irrigation solution. NY State Dent J 2008:74:31-3.
44. Bowden GH, Hamilton IR. Survival of oral bacteria. Grit Rev Oral Biol Med 1998:9:54-84.
45. Svensater G, Bergenholtz G. Biofilms in endodontic infections. Endod Topics 2004:9:27-36. 78.
46. Nair PN, Henry S, Gano V, Vera J. Microbial status of apical root canal system of human
mandibular first molars with primary apical periodontitis after 'one-visit' endodontic treat- 79.
ment. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005:99:231-42.
47. Wu MK, Dummer P, Wesselink P. Gonsequences of and strategies to deal with residual post- 80.
treatment root canal infection. Int Endod J 2006:39:343-56.
48. Noiri Y, Ehara A, Kawahara T, et al. Participation of bacterial biofilms in refractory and 81.
chronic periapical periodontitis. j Endod 2002:28:679-83.
49. Stoodley LH, Gosterton JW, Stoodley P. Bacterial biofilms: from the natural environment to 82.
infectious diseases. Nat Rev Microbiol 2004:2:95-108.
50. Glegg MS, Vertucci FJ, Walker G, et al. The effect of exposure to irrigant solutions on apical
dentine biofilms in vitro. J Endod 2006:32:434-7. 83.
51. Dunavant TR, Regan JD, Glickman GN, et al. Gomparative evaluation of endodontic irrig-
ants against Bnterococcus faecalis biofilms. J Endod 2006:32:527-31. 84.
52. Giardino L, Ambu E, Savoldi E, et al. Gomparative evaluation of antimicrobial efficacy of
sodium hypochlorite, MTAD, and Tetraclean against Enterococcus faecalis biofilm. J Endod 85.
2007:33:852-5.
53. Peters OA, Barbakow F. Effect of irrigation on debris and smear layer wails prepared by two 86.
rotary techniques. A scanning electromicroscopic study. J Endod 2000:26:6-10.
54. Heard F, Walton RE. Scanning electron microscope study comparing four root canal prepa-
ration techniques in small curved canals. Int Endod J 1997:30:323-31.
55. Torabinejad M, Handysides R, Khademi A, Bakland IK. Glinical implications of the smear layer
in endodontics: a review. Oral Surg Oral Med Oral Path Oral Radiol Endo 2002:94:658-66.
56. Sjogren U, Figdor D, Persson S, Sundqvist G. Infiuence of infection at the time of root fill-
ing on the outcome of endodontic treatment of teeth with apical periodontitis. Int Endod J
1997:30:297-306.
57. Peters LB, Wesselink PR, Buijs JF, van Winkelhoff AJ. Viable bacteria in root dentinal tubules
of teeth with apical periodontitis. J Endod 2001;27:76-81.
58. Torabinejad M, Gho Y, Khademi AA, Bakland LK, Shabahang S. The effect of various concen-
trations of sodium hypochlorite on the ability of MTAD to remove the smear layer. J Endod
2003:29:233-9.
59. Tay FR, Pashley D, Loushine RJ, et al. Ultrastructure of smear layer-covered intraradicular
dentin after irrigation with BioPure MTAD. J Endod 2006:32:218-21.
60. Tay FR, Hosoya Y, Loushine RJ, et al. Ultrastructure of intraradicular dentin after irrigation
with BioPure MTAD. II. The consequence of obturation with an epoxy resin-base sealer. J
Endod 2006:32:473-7.
61. De-Deus G, Reis G, Fidel S, et al. Dentin demineralization when subjected to BioPure
MTAD: a longitudinal and quantitative assessment. J Endod 2007: 33:1364-8.
Machnick T, Torabinejad M, Munoz GA, et al. Effect of MTAD on fiexural strength and
modulus of elasticity of dentin. J Endod 2003:29:747-50.
Lemann J Jr, Litzow JR, Lennon EJ. The effects of chronic acid loads in normal man: further
evidence for the participation of bone mineral in the defense against chronic metabolic
acidosis. J Giin Invest 1966:45:1608-14.
Wang JD, Hume WR. Diffusion of hydrogen ion and hydroxyl ion from various sources
through dentine. Int Endod J 1988:21:17-26.
Gamps J, Pashley DH. Buffering action of human dentin in vitro. J Adhes Dent 2000:2:39-50.
Haapasalo M, Qian W, Portenier I, et al. Effects of dentine on the antimicrobial properties
of endodontic medicaments. J Endod 2007:33:917-25.
Haapasalo HK, Siren EK, Waltimo TM, et al. Inactivation of local root canal medicaments
by dentine: an in vitro study Int Endod J 2000:33:126-31.
Portenier I, Waltimo T, 0rstavik D, Haapasalo M. Killing of Enterococcus faecalis by MTAD
and chlorhexidine digluconate with or without cetrimide in the presence or absence of
dentine powder or BSA. J Endod 2006:32:138-41.
Mjor IA, Moorhead JE, Dahi JE. Reasons for replacement of restorations in permanent teeth
in general dental practice. Int Dent J 2000:50:361-6.
Garrilho MR, Tay FR, Pashley DH, et al. Mechanical stability of resin-dentin bond compo-
nents. Dent Mat 2005:21:232-41.
De Munck J, Van Landuyt K, Peumans M, et al. A critical review of the durability of adhe-
sion to tooth tissue: methods and results. J Dent Res 2005:84:118-32.
Frankenberger R, Pashiey DH, Reich SM, et al. Gharacterisation of resin-dentine interfaces
by compressive cyclic loading. Biomater 2005:26:2043-52.
Wang Y, Spencer P. Hybridization efficiency of the adhesive/dentine interface with wet
bonding. J Dent Res 2003:82:141-5.
Wang Y, Spencer P. Gontinuing etching of an all-in-one adhesive in wet dentine tubules. J
Dent Res 2005:84:350-4.
Yiu GK, King NM, Pashley DH, et al. Effect of resin hydrophilicity and water storage on
resin strength. Biomaterials 2004:25:5789-96.
Garrilho MR, Garvalho RM, Tay FR, et al. Durability of resin-dentin bonds related to water
and oil storage. Am J Dent 2005:18:315-9.
Hashimoto M, Ohno H, Sano H, et al. In vitro degradation of resin-dentin bonds analyzed
by microtensile bond test, scanning and transmission electron microscopy. Biomater 2003:
24:3795-803.
Pashley DH, Tay FR, Yiu G, et al. Gollagen degradation by host-derived enzymes during ag-
ing. J Dent Res 2004:83:216-21.
Martin-De Las Heras S, Valenzuela A, Overall GM. The matrix metalloproteinase gelatinase
A in human dentine. Arch Oral Biol 2000:45:757-65.
Sulkala M, Larmas M, Sorsa T, et al. The localization of matrix metalloproteinase-20 (MMP-
20, enamelysin) in mature human teeth. J Dent Res 2002:81:603-7.
Sulkala M, Tervahartiala T, Sorsa T, et al. Matrix metalloproteinase-8 {MMP-8) is the major
collagenase in human dentin. Arch Oral Biol 2007: 52: 121-7.
Mazzoni A, Pashley DH, Nishitani Y, et al. (2006) Reactivation of quenched endogenous
proteolytic activities in phosphoric acid-etched dentine by etch-and-rinse adhesives Biom-
ater 2006:27:4470-6.
Machnick T, Effect of MTAD on the bond strength to enamel and dentin. J Endod 2003:29:
818-21.
Garcia-Godoy F, Loushine RJ, Itthagarun A, et al. Application of biologically-oriented den-
tin bonding principles to the use of endodontic irrigants. Am J Dent 2005:18:281-90.
Wachlarowicz AJ, Joyce AP, Roberts S, et al. Effect of endodontic irrigants on the shear bond
strength of epiphany sealer to dentin. J Endod 2007:33:152-5.
Zhang W, Torabinejad M, Li Y. Evaluation of cytotoxicity of MTAD using the MTT-tetrazo-
lium method. J Endod 2003:29:654-7.
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